The present invention relates generally to combine harvesters and, more particularly, to a rotary cleaning mechanism in combines for cleaning unwanted residue, such as chaff, straw, etc., from threshed grain.
Conventional cleaning systems clean threshed grain by blowing air through a set of planar sieves utilizing gravitational forces to urge cleaned grain through the sieve openings. With the advent of higher capacity threshing and separating mechanisms, such as rotary axial flow combines, the capacity for threshing grain has increased beyond the capacity of conventional cleaning systems to clean the grain. Accordingly, it is desirable to increase both the capacity and the efficiency of cleaning systems in combine harvesters so as not to limit the throughput capability of the combine.
The mounting of a rotary cleaning mechanism within the comfines of a combine base unit requires that the drive mechanism for the individually rotatable components of the cleaning mechanism be compactly situated. Further complicating the drive arrangement is a requirement that each of the individually driven components; namely, the fan, infeed auger, impeller and cleaning cylinder, be driven at different rotational speeds for optimal cleaning results. Also, a mechanism for reciprocating the cleaning shoes during rotation of the cleaning cylinder needs to be operatively powered by the drive mechanism.